Question

Why might the P-wave be the same height between Leads while QRS and T are bigger in Lead II?

Answer 1

The right and left atria or upper chambers make the first wave called a "P wave". This is followed by a flat line that displays that the electrical impulse goes to the bottom chambers or the ventricles. The right and left ventricles make the next wave called a "QRS complex". The final wave is called the "T wave" represents electrical recovery or return to a resting state for ventricles.

Lead I in ECG records the electrical differences between the right and left arm electrodes.

Lead II in ECG records electrical differences between the left leg and right arm electrodes. This is the bipolar lead and probably, for this reason, the QRS and T waves are bigger in Lead II.